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Rebreather Evaluation – Part 4: The Megalodon

The Megalodon is made by Inner Space Systems, and is the brainchild of ISC owner and CEO Leon Scamahorn. I first got a chance to see the Megalodon on the Nautilus Explorer after a friend had bought one, and I was very impressed. It is a very serious looking unit and has a distinctively hand-made, one-off feel to it.

Unlike the other units I evaluated, the Meg is completely modular. There there are some standard configurations, but in the end, nearly everything is an optional addon to the basic envelope. It is built on the foundation of the outer housing, which is essentially an aluminum cylinder containing the standard axial scrubber, oxygen cells and electronics package. Two nice displays are attached to the head, as well as an optional HUD. Since the outer housing is constructed of aluminum, it is very rigid, giving you a number of options when it comes to attaching your oxygen and diluent bottles. The one I like best is the Tiger Gear setup, whitch provides a very elegant and tough mount.

The hoses, ADV and front-mounted counterlungs are all extremely well made, and the design on the unit gives it a very low profile. Leon spent 12 years with the Army Special Forces and it’s clear that he has built the unit with his military background in mind. The first thought that comes to mind when you see the Megalodon is that it is both incredibly rugged, and user friendly. The displays are large and easy to read, and apparently they tested the resiliency of the unit by dropping it from five feet onto a concrete floor. When a component broke, it was made stronger. When they were all done, the Meg was fine, but the concrete floor was broken. Did I mention that this unit is built to be tough?

The list of things I like about the Megalodon is fairly long and detailed, but I’ll try to sum it up as best as I can:

Solid construction

High quality materials – Alluminum, ballistic nylon, acetal, etc.

Water traps EVERYWHERE

Corrosion resistant

Easily readable handsets

Low porfile

No housing / shell nonsense

Batteries sealed off from the breathing loop

Modular design – Mount any cylinders, use any backplate / wing.

Ability to use any scrubber you like – Megalodon, CisLunar, Extendair, and an SMI Prism.

There aren’t really many things I don’t like about the meg, but there are a few points I think might make it a little better.

I wish it had a radial scrubber. While you can use the CisLunar or SMI Prism scrubbers, you have to purchase these seperately if you can find them.

While the electronics package is great, it is only a loop controller. I wish the unit had the ability to do integrated deco calculations. This feature is coming in the next version of the software, but I would imagine that it will be a costly upgrade.

I would like to see a slightly more readable HUD. It is only one LED that blinks codes for each sensor. This is fine once you get used to it, but the SMI Prism has a slightly better HUD in my opinion.

That’s about it. Like I said, these aren’t really complaints, but more of a wish list. The Meg is, after all, the unit I decided to get for myself.

The following are the additional options that I decided to get on my Meg:

ADV (Automatic Diluent valve)

HUD

Mixed Gas Bypass – A must for TRIMIX, it provides the option to plumb in off-board gases

As I believe it will result in a system that runs with much less moisture, I have every intention of trying to find a CisLunar radial scrubber at some point. This is by far, the most advanced scrubber design ever seen in the world of rebreathers. For the time being, however, the standard ISC Axial scrubber should be just fine.

I was reading the article” Rebreather Evaluation – Part 4: The Megalodon” dated Jan 24, 2006.
It would be nice to have a ~3 year followup on the author’s experiences after buying the Meglodon. Does Cliff still write for you?

I am an avid diver with nearly 200 dives on air or nitrox. I have somewhere around 20 dives on my SCR Dolphin which has left me wanting two things: 1 – a Closed Circuit Rebreather and 2 – different dive buddies. All too often there have been things to see or places that I want to go or things I want to do underwater and not enough air to do them or no buddy to do them with.
I have looked at the PRISM, the Evolution and the Megalodon. There was a lot of talk and planning going on a few years back on an Open Revolution Rebreather that would encompass all of the good and none of the bad from different Rebreathers but I have not heard any more on that Rebreather.
I have heard that the Meg has one disadvantage that was not mentioned. Perhaps it was not mentioned due to it not seeming to be an issue by the author. Or perhaps the issue I have heard is not an issue after all. What I heard is that the Meg electronics is inside the breathing loop and therefore the loop must be opened to turn the Meg on and again to turn it off. Is this fact or fiction? If this is fact, is this unlike other Rebreathers? Not many posts go down far enough to show how the electronics are turned on or off.

It is a fact that the electronics are inside the breathing loop, and that you must remove the head to turn it on. As to if it’s a downside or not, who’s to say. I tend to fire it up in the beginning of the day and leave it on until I’m ready to go home, so it’s not a big deal. The head needs to come off to let all the condensation dry off anyhow. There have also been a couple of fatalities caused by people forgetting to turn on their rebreather before entering the water. It’s like anything else in life; it comes with some advantages and disadvantages. In practice, however, it’s really not as much of a bother as I thought it would be.